A sports foot is generally designed as a one-piece leaf spring made from a fiber-reinforced plastic. The binding to a socket, which is also intended to be possible in below-knee prostheses, has the effect that, during loading, the tip of the leaf spring not only moves upward with respect to the socket, i.e. in the vertical direction, but also moves forward as a result of a flexion of the spring. When the foot is set down, this has the effect that the leg is pressed rearward in relation to the ground. Moreover, when the energy stored in the spring is released, a posteriorly directed component may arise, with the result that the direction of the energy release does not correspond 100% to the direction in which the athlete is running.
Under the trade name Flex-Run, the company Össur markets a sports foot with a spring which is bent in a C shape and on the upper end of which an attachment adapter is secured.
Under the trade name “endolite Blade XT”, the company Chas A Blatchford & Sons Ltd. markets a prosthetic foot for amateur athletes and runners, having a forefoot spring which has a substantially horizontal head section and a one-piece spring with an outwardly convex shape, said spring being divided into two parts in the lower area by a slit. In the front area of the spring, a sole protection and a heel spring are fastened by way of two screws; the spring stiffness of the heel spring can be set using a wedge. The heel spring has a less flexible reaction as a consequence of inserting the heel wedge. A proximal adapter is guided displaceably in a receiving slit in a securable manner.
The company Freedom Innovations markets a sports foot under the trade name “Nitro Running Foot”, with a vertical receiving area on which a proximal adapter is secured. From the proximal adapter, a one-piece leaf spring extends in an arc shape as far as a foot-strike area. The special leaf spring slopes gently upward.